Timer that invokes a Cloud Functions function

Timer is a trigger that calls a Cloud Functions function on a schedule. The schedule is set as a cron expression. The cron expression uses UTC+0.

A timer needs a service account to invoke a function.

For more information about creating a timer, see Creating a timer that invokes Cloud Functions.

Cron expression formatCron expression format

The fields in a cron expression are ordered as follows: Minutes Hours Day-of-month Month Day-of-week Year.

Possible field valuesPossible field values

Special charactersSpecial characters

You can use the following special characters in cron expressions:

• *: Selects all values in the field.

  * in the Minutes field: Trigger fires every minute.

• ?: Selects any field value. You cannot specify Day of month and Day of week at the same time. If you have entered a value in one of these fields, put ? in the other one.

  10 in Day of month and ? in Day of week: Trigger fires on the 10th day of each month.

• -: Selects a range of values.

  10-12 in Hours: Trigger fires at 10 a.m., 11 a.m., and 12 p.m.

• ,: Selects multiple values.

  MON,WED,FRI in Day of week: Trigger fires on Monday, Wednesday, and Friday.

• /: Increments the value.

  0/15 in Minutes: Trigger fires at 0, 15, 30, and 45 minutes past each hour.

• L: This character has different meanings in the two fields it is valid for:

  • In the Day of month field, it means the last day of the month.
  • In the Day of week field, it means the last day of the week, 7 (Saturday, SAT).

  L in Day of month: Trigger fires on January 31, February 28, and so on.

• W: Selects the weekday nearest to the specified date.

  15W in Day of month: Trigger fires on the weekday nearest to the 15th day of the month. If the 15th day falls on Saturday, the trigger fires on Friday the 14th.

  Note

  L and W in the Day of month field can also merge into the LW combination, firing the trigger on the last weekday of the month.

• #: Selects the Nth day of the month.

  6#3 in Day of week: Trigger will fire on the third Friday of the month (6 for Friday; 3 for third Friday of the month).

Examples of cron expressionsExamples of cron expressions

Roles required for timers to run correctlyRoles required for timers to run correctly

• To create a timer, you need a permission for the service account under which the timer runs the operation. This permission comes with the iam.serviceAccounts.user and editor roles or higher.
• To run a timer, the service account needs the functions.functionInvoker role for the folder containing the function called by the timer.

Read more about access management.

Timer message formatTimer message format

After the trigger is activated, it sends the following message to the function:

{
  "messages": [
    {
      "event_metadata": {
        "event_id": "a1s41g2n5g0o********",
        "event_type": "yandex.cloud.events.serverless.triggers.TimerMessage",
        "created_at": "2019-12-04T12:05:14.227761Z",
        "cloud_id": "b1gvlrnlei4l********",
        "folder_id": "b1g88tflru0e********"
      },
      "details": {
        "trigger_id": "a1sfe084v4se********",
        "payload": "payload-message"
      }
    }
  ]
}

Use casesUse cases

• Yandex Tracker: data export and visualization
• Monitoring the status of geographically distributed devices
• Scheduled instance group scaling with the management console, CLI, and API
• Sensor reading monitoring and event notifications
• Deploying a fault-tolerant architecture with preemptible VMs
• Running scheduled computations in DataSphere

See alsoSee also

• Timer to run a Serverless Containers container
• Timer that sends messages to WebSocket connections